3,534 research outputs found
Magnetized strange quark matter in a quasiparticle description
The quasiparticle model is extended to investigate the properties of strange
quark matter in a strong magnetic field at finite densities. For the
density-dependent quark mass, self-consistent thermodynamic treatment is
obtained with an additional effective bag parameter, which depends not only on
the density but also on the magnetic field strength. The magnetic field makes
strange quark matter more stable energetically when the magnetic field strength
is less than a critical value of the order Gauss depending on the QCD
scale . Instead of being a monotonic function of the density for the
QCD scale parameter MeV, the effective bag function has a maximum
near fm. The influence of the magnetic field and the QCD
scale parameter on the stiffness of the equation of state of the magnetized
strange quark matter and the possible maximum mass of strange stars are
discussedComment: 10 pages, 7 figure
Co-production of single cell oil and gluconic acid using oleaginous Cryptococcus podzolicus DSM 27192
Background: The co-production of single cell oil (SCO) with value-added products could improve the economic viability of industrial SCO production. The newly isolated oleaginous yeast Cryptococcus podzolicus DSM 27192 was able to co-produce SCO intracellularly and gluconic acid (GA) extracellularly. In this study, the metabolic regulation of carbon distribution between SCO and GA through process optimization was comprehensively investigated.
Results: The carbon flow distribution between SCO and GA was significantly influenced by the cultivation conditions, such as nitrogen sources, glucose concentration and dissolved oxygen concentration. It was found that organic nitrogen sources were beneficial for SCO accumulation, while GA production was decreased. Dissolved oxygen concentration (DOC) was found to enhance SCO accumulation, while high glucose concentration was more favorable for GA accumulation. Hence, a two-stage DOC or glucose concentration-controlled strategy was designed to improve cell growth and direct carbon distribution between SCO and GA. Moreover, C. podzolicus DSM 27192 could degrade its stored lipids to synthesize GA in the late stationary phase, although considerable amounts of glucose remained unconsumed in the culture medium, indicating the importance of fermentation time control in co-production systems. All these observations provide opportunity to favor either the production of SCO or GA or rather their simultaneous production.
Conclusions: Co-production of SCO and GA by C. podzolicus DSM 27192 can improve the economical value for microbial lipid-derived biodiesel production. Moreover, the results of the proposed co-production strategy might give guidance for other co-production systems
First Census of Gas-phase Metallicity Gradients of Star-forming Galaxies in Overdense Environments at Cosmic Noon
We report the first spatially resolved measurements of gas-phase metallicity
radial gradients in star-forming galaxies in overdense environments at
. The spectroscopic data are acquired by the \mg\ survey, a Hubble
Space Telescope (HST) cycle-28 medium program. This program is obtaining 45
orbits of WFC3/IR grism spectroscopy in the density peak regions of three
massive galaxy protoclusters (BOSS 1244, BOSS 1542 and BOSS 1441) at .
Our sample in the BOSS 1244 field consists of 20 galaxies with stellar-mass
ranging from to \Msun\ , star formation rate (SFR) from
10 to 240 \Msun\,yr, and global gas-phase metallicity (\oh) from 8.2 to
8.6. At confidence level, 2/20 galaxies in our sample show positive
(inverted) gradients -- the relative abundance of oxygen increasing with
galactocentric radius, opposite the usual trend. Furthermore, 1/20 shows
negative gradients and 17/20 are consistent with flat gradients. This high
fraction of flat/inverted gradients is uncommon in simulations and previous
observations conducted in blank fields at similar redshifts. To understand
this, we investigate the correlations among various observed properties of our
sample galaxies. We find an anticorrelation between metallicity gradient and
global metallicity of our galaxies residing in extreme overdensities, and a
marked deficiency of metallicity in our massive galaxies as compared to their
coeval field counterparts. We conclude that the cold-mode gas accretion plays
an active role in shaping the chemical evolution of galaxies in the
protocluster environments, diluting their central chemical abundance, and
flattening/inverting their metallicity gradients.Comment: 13 pages, 6 figures, 1 table. Accepted for publication in ApJ
The SVOM gamma-ray burst mission
We briefly present the science capabilities, the instruments, the operations,
and the expected performance of the SVOM mission. SVOM (Space-based multiband
astronomical Variable Objects Monitor) is a Chinese-French space mission
dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade. The SVOM
mission encompasses a satellite carrying four instruments to detect and
localize the prompt GRB emission and measure the evolution of the afterglow in
the visible band and in X-rays, a VHF communication system enabling the fast
transmission of SVOM alerts to the ground, and a ground segment including a
wide angle camera and two follow-up telescopes. The pointing strategy of the
satellite has been optimized to favor the detection of GRBs located in the
night hemisphere. This strategy enables the study of the optical emission in
the first minutes after the GRB with robotic observatories and the early
spectroscopy of the optical afterglow with large telescopes to measure the
redshifts. The study of GRBs in the next decade will benefit from a number of
large facilities in all wavelengths that will contribute to increase the
scientific return of the mission. Finally, SVOM will operate in the era of the
next generation of gravitational wave detectors, greatly contributing to
searches for the electromagnetic counterparts of gravitational wave triggers at
Xray and gamma-ray energies.Comment: 13 pages, 5 figures, published by PoS, proceedings of the conference
Swift: 10 Years of Discovery, 2-5 December 2014, La Sapienza University,
Rome, Ital
Relation between millimeter wavelengths emission and high-energy emission for active galactic nuclei
After comparing the flux densities of a sample of active galactic nuclei
detected by energetic gamma-ray experiment telescope at 90 and 230 GHz with the
-ray emissions detected by Compton Gamma Ray Observatory and x-ray
emission, a strong correlation between the emissions at the millimeter
wavelength and the -ray emission is found. The average flux density of
x-ray is almost proportional to the average flux density at the millimeter
wavelength for quasars detected by energetic gamma-ray experiment telescope,
which strongly supports the previous idea that the x-ray emissions of this kind
sources are mainly produced by Synchrotron Self-Compton process.Comment: 6 pages, Chinese Physics Letters in pres
On Vanishing Theorems For Vector Bundle Valued p-Forms And Their Applications
Let be a strictly increasing function
with . We unify the concepts of -harmonic maps, minimal
hypersurfaces, maximal spacelike hypersurfaces, and Yang-Mills Fields, and
introduce -Yang-Mills fields, -degree, -lower degree, and generalized
Yang-Mills-Born-Infeld fields (with the plus sign or with the minus sign) on
manifolds. When and
the -Yang-Mills field becomes an ordinary Yang-Mills field,
-Yang-Mills field, a generalized Yang-Mills-Born-Infeld field with the plus
sign, and a generalized Yang-Mills-Born-Infeld field with the minus sign on a
manifold respectively. We also introduce the energy functional (resp.
-Yang-Mills functional) and derive the first variational formula of the
energy functional (resp. -Yang-Mills functional) with
applications. In a more general frame, we use a unified method to study the
stress-energy tensors that arise from calculating the rate of change of various
functionals when the metric of the domain or base manifold is changed. These
stress-energy tensors, linked to -conservation laws yield monotonicity
formulae. A "macroscopic" version of these monotonicity inequalities enables us
to derive some Liouville type results and vanishing theorems for forms with
values in vector bundles, and to investigate constant Dirichlet boundary value
problems for 1-forms. In particular, we obtain Liouville theorems for
harmonic maps (e.g. -harmonic maps), and Yang-Mills fields (e.g.
generalized Yang-Mills-Born-Infeld fields on manifolds). We also obtain
generalized Chern type results for constant mean curvature type equations for
forms on and on manifolds with the global doubling property
by a different approach. The case and is due to Chern.Comment: 1. This is a revised version with several new sections and an
appendix that will appear in Communications in Mathematical Physics. 2. A
"microscopic" approach to some of these monotonicity formulae leads to
celebrated blow-up techniques and regularity theory in geometric measure
theory. 3. Our unique solution of the Dirichlet problems generalizes the work
of Karcher and Wood on harmonic map
Geometric Control of Human Stem Cell Morphology and Differentiation
During tissue morphogenesis, stem cells and progenitor cells migrate, proliferate, and differentiate, with striking changes in cell shape, size, and acting mechanical stresses. The local cellular function depends on the spatial distribution of cytokines as well as local mechanical microenvironments in which the cells reside. In this study, we controlled the organization of human adipose derived stem cells using micro-patterning technologies, to investigate the influence of multi-cellular form on spatial distribution of cellular function at an early stage of cell differentiation. The underlying role of cytoskeletal tension was probed through drug treatment. Our results show that the cultivation of stem cells on geometric patterns resulted in pattern- and position-specific cell morphology, proliferation and differentiation. The highest cell proliferation occurred in the regions with large, spreading cells (such as the outer edge of a ring and the short edges of rectangles). In contrast, stem cell differentiation co-localized with the regions containing small, elongated cells (such as the inner edge of a ring and the regions next to the short edges of rectangles). The application of drugs that inhibit the formation of actomyosin resulted in the lack of geometrically specific differentiation patterns. This study confirms the role of substrate geometry on stem cell differentiation, through associated physical forces, and provides a simple and controllable system for studying biophysical regulation of cell function
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